1. Technical Field
The present invention relates to a component placing head and a component placing method that have a plurality of component holding members, capture an image of a component held by each component holding member, recognize a holding posture of the component, and place the component on a circuit board on basis of a result of the recognition.
2. Background Art
In recent years, markets have been increasing their demands for miniaturization, high performance, and reduction in cost of electronic equipment that contains electronic circuits formed by placement of electronic components as a plurality of components on circuit boards.
In an electronic component placing apparatus having a head, as an example of a component placing head, the plurality of electronic components are placed by the head on the circuit boards held on a stage and electronic circuits are thereby manufactured. In such an electronic component placing apparatus, holding postures of the electronic components held by the head, placement positions of the electronic components on the circuit board, and the like, are recognized by use of image-pickup devices provided on the stage or on the head, or the like, and the electronic components are placed on the circuit board on the basis of a result of the recognition (see Japanese unexamined Patent Publication No. 9-307297, for example).
In order to meet the demands from the markets, on the other hand, electronic component placing apparatus have been desired to cope with persistent miniaturization of the electronic components and the circuit boards and to perform placement with high density and high accuracy of the electronic components on the circuit boards and have been desired to achieve a decrease in time span required for the placement so as to fulfill efficient placement and a reduction in the manufacturing cost of electronic circuits.
Hereinbelow, an image-pickup device 210 provided in a head 200 in such a conventional electronic component placing apparatus will be described with reference to a fragmentary enlarged schematic explanatory view of the head 200 shown in FIG. 7. The head 200 has eight suction nozzles 201 as component holding members, arranged in a row, and FIG. 7 shows a section of the head 200 taken along a plane orthogonal to a direction of the arrangement.
As shown in FIG. 7, the head 200 has the eight suction nozzles 201 capable of sucking and holding electronic components 1 at extremities of the nozzles, and each suction nozzle 201 is supported by a head frame 202 so as to be capable of moving up and down along a central axis of the nozzle (in vertical directions in FIG. 7) and capable of rotating about the central axis.
As shown in FIG. 7, the image-pickup device 210 has a camera 211 that is provided to the left of the suction nozzle 201 in the drawing and that is capable of capturing an image of the electronic component 1 sucked and held by the suction nozzle 201, from underneath the electronic component in the drawing via two reflecting mirrors 212 and 213 placed on an optical axis of the camera. The image-pickup device 210 also has a linear guide rail 214 that is provided along the direction of the arrangement of the suction nozzles 201 to the upper left of the suction nozzle 201 in the drawing and that is fixed to the head frame 202. The camera 211 is supported by the head frame 202 through medium of the linear guide rail 214 so as to be capable of sliding along the linear guide rail 214, i.e., along the direction of the arrangement of the suction nozzles 201. A sliding device 215 for sliding the camera 211 along the linear guide rail 214 is fixed to the head frame 202 in neighborhood of a location where the linear guide rail 214 is installed.
When images of the electronic components 1 held by the suction nozzles 201 are captured by the image-pickup device 210, an image of the electronic component 1 held by each suction nozzle 201 is sequentially captured from underneath via the reflecting mirrors 212 and 213 while the camera 211 is slid by the sliding device 215 along the linear guide rail 214. Each image captured in this manner is subjected to recognition processing in a control unit, or the like, provided in the head 200 and is recognized as a suction holding posture of each electronic component 1 relative to each suction nozzle 201. The suction holding posture is then corrected by rotating of the suction nozzle 201, or the like, so that the recognized suction holding posture coincides with a placement posture relative to a circuit board, and the electronic component 1 is thereafter placed on the circuit board.
In the head 200 having the above structure, however, an image of the electronic component 1 held by the suction nozzle 201 is captured from underneath the electronic component 1, and it is therefore impossible to recognize a suction holding posture of the electronic component 1 with respect to the direction along the central axis of the suction nozzle 201 (i.e., the vertical direction in FIG. 7). For example, an electronic component 1 that is a minute electronic component such as a chip component is prone to be sucked and held in a position angled to the extremity of a suction nozzle 201 (what is called an angled position), it is difficult to recognize such a position on the basis of an image captured from underneath, and placement on a circuit board with such a position unrecognized may cause an error in the placement of the electronic component 1 on the circuit board or may cause a problem in that high-accuracy placement of electronic components cannot be achieved even if the placement error is avoided.
In the head 200, the sliding device 215 is provided on the head frame 202 in the neighborhood of the linear guide rail 214 and of the camera 211. Vibrations accompanying operation of the sliding device 215 are therefore prone to be transmitted through the linear guide rail 214 to the camera 211, and this causes a problem in that the camera 211 influenced by the vibrations cannot capture a high-accuracy image of an electronic component 1. An increase in the sliding velocity of the camera 211 slid by the sliding device 215, for the purpose of a decrease in a time span required for the placement of an electronic component 1 by the head 200, strengthens the transmitted vibrations and makes the above problem more noticeable, while a decrease in the sliding velocity for the purpose of a reduction in the vibrations fails to allow the decrease in the time span required for the placement and fails to allow efficient operation for placing electronic components.
In a head 200 provided with a board recognizing device for recognizing placement positions, or the like, for electronic components 1 on a circuit board, for example, the electronic components 1 can be placed with reliable recognition of the placement positions on the circuit board; however, recognition accuracy required of the board recognizing device differs with the required accuracy in placement of electronic components 1. Though a head 200 that is provided with a board recognizing device having a high recognizing accuracy so as to address the high-accuracy placement of electronic components is capable of addressing high-accuracy placement, a narrowed recognizable field of view of the device causes a problem, for example, in that placement of an electronic component 1 which does not require high-accuracy placement may rather increase a time span required for recognition and may lower a placing efficiency.
In order to address such high-accuracy placement of electronic components, it is necessary to capture a clear image of a placement surface of a component sucked and held by a suction nozzle. Though simple capture of the image with illumination of the placement surface of the component may address capture of images of conventional general-purpose components, the simple capture for miniaturized components, components with diversified shapes, and the like, may cause non-uniform illuminance, or the like, on their placement surfaces having miniaturized shapes, special shapes, and the like, and may thereby cause a problem in that images of the components cannot be captured clearly and in that such electronic components cannot be placed with a high accuracy.
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a component placing head and a component placing method that have a plurality of component holding members, capture an image of a component held by each component holding member, recognize a holding posture of the component, and place the component on a circuit board on the basis of a result of the recognition, the component placing head and the component placing method being capable of performing the recognition with a high efficiency and a high accuracy.